Experiments are designed to use mouse teratoma cells as source material for analysis of events of cellular differentiation. Teratoma cells, demonstrated to be multipotential, will be studied with an aim of directing differentiation along specific pathways by the appropriate use of inductive tissues, selective environments, and genetic variants. In addition to study of existing teratomas, new ones will be induced in a variety of strains to permit identification of cells in experiments involving transplantation or mixing in tissue culture. Induction of partially restricted tumor cell lines will be attempted by appropriate choice of starting material. Functional tests for differentiation will include capacity for specific synthesis of tissue-specific molecules (e.g. hemoglobin, immunoglobulin) as well as the capacity to induce differentiation in appropriate responding tissues (e.g. metanephrogenic mesenchyme). Where feasible, clonally-derived subcultures of individual teratomas will be prepared. Clones will be expanded and representative cultures frozen and stored for subsequent recovery and use. It is hoped that the proposed experiments will contribute to an understanding of the mechanisms controlling both normal and abnormal growth and differentiation. The undersigned agrees to accept responsibility for the scientific and technical conduct of the project and for provision of required progress reports if a grant is awarded as the result of this application.